React div onKeyDown event does not fire


With a very simple DIV, this key-binding does not work. A mouse event works, binding onKeyDown to an INPUT works (but then I cannot add children, which is what I need), and from what I see, HTML5 and also React perfectly allows binding key events to plain divs. What gives?

let make = () => {
  let onKeyDown = (event) => {

  <div onKeyDown>{React.string("Type something")}</div>

Linked to from an index.html, JS packed together with webpack, loaded from file:///home/kero/blah/index.html)

It should be contenteditable